1. Field of the Invention
An improved process for the manufacture of extended gel free sulfonated elastomeric products includes the formation of a homogeneous mixture of fillers with the acid form of the sulfonated polymer prior to the neutralization of the acid form of the sulfonated polymer with a basic material thereby resulting in a composition having improved physical properties.
2. Description of the Prior Art
This invention relates to a unique and novel improved process for forming extended elastomeric blends of sulfonated elastomeric polymers.
Recently a new class of sulfonated polymers has been described in a number of U.S. Pat. Nos. 3,642,728; 3,836,511; 3,870,841 and 3,847,854, herein incorporated by reference.
U.S. Pat. No. 3,642,728 teaches a method of selective sulfonation with an SO.sub.3 donor of olefinic unsaturation sites of an elastomeric polymer to form an acid form of a sulfonated elastomeric polymer. U.S. Pat. No. 3,642,728 recognized that the free sulfonic acid of the sulfonated elastomer decomposed at conventional rubber processing temperatures and thereby required that a substantial portion of the sulfonic acid be neutralized prior to isolation. It further recognized that optimum thermal stability is reached at total neutralization; however, the melt viscosities of the fully neutralized systems are extremely high. Consequently the fully neutralized systems are extremely difficult, if not impossible, to process in conventional equipment under conventional conditions.
U.S. Pat. No. 3,836,511 teaches an improved method of sulfonation of the olefinic sites of the elastomeric polymer, wherein the improved sulfonating agent is an acyl sulfate. The acid form of the sulfonated elastomeric polymer is neutralized with an organic amine to produce a neutralized sulfonated elastomeric polymer having rather inferior physical properties due to a low degree of ionic association.
The extremely high viscosities of the compositions of U.S. Pat. No. 3,642,728 and the poor physical properties of the compositions of U.S. Pat. No. 3,836,511 limit their usefulness.
U.S. Pat. Nos. 3,870,841 and 3,847,854 teach a method of plasticization of the polymeric backbone of a neutralized sulfonated polymer. The plasticizing agent is incorporated into the sulfonated polymer by hot mixing the neutralized sulfonated polymer with the plasticizing agent. Although, the rheological properties are improved, the incorporation of these plasticizing agents into the neutralized sulfonated polymers is extremely difficult and usually results in a general decrease in physical properties.
The aforementioned patents teach methods of compounding the additives into the neutralized sulfonated elastomeric polymer under high heat and shear conditions or the use of an organic amine neutralizing agent thereby resulting in compositions either having poor rheological or physical properties.
The present invention teaches a new improved process for forming improved compositions of matter which includes forming a homogeneous mixture of an acid form of a sulfonated elastomeric polymer, a mineral or a carbon black filler, and a non-polar process oil, and subsequently neutralizing the sulfonated polymer, wherein the resultant extended elastomeric blends have improved physical properties while maintaining acceptable rheological properties.